ITU-T (International Telecommunication Union Telecommunication Standardization Sector) G. 711 (Non-patent literature 1) is an international standard of voice-frequency signal encoding. ITU-T G. 711 uses non-uniform pulse code modulation (PCM) as the encoding mode and prescribes two types of non-linear quantization modes, μ law and A law. Hereafter, a voice-frequency signal is referred to as a voice signal.
MPEG-4 established by the ISO/IEC JTC 1/SC 29/WG 11 is an international standard for video and audio encoding, and its third part stipulates an audio lossless encoding technology and the like (Non-patent literature 2).